The present invention relates to vehicle remote starting systems, and more particularly, to electronic circuitry for bypassing the electronic anti-theft system of a vehicle to permit starting of the engine from a remote location. The electronic module of the present invention will be referred to as an electronic pass-key module (PK module) throughout the description.
Vehicle manufacturers are installing anti-theft systems on many vehicles. Some of them are now relying on the wireless transmission of a coded signal from a transponder embedded into the grip of the mechanical ignition key, thus providing an electronic key, in order to enable starting of the engine and driving of the vehicle. Typically, to drive the vehicle the electronic key is inserted into the ignition cylinder and the electronic ID code is read by a short range transceiver usually located near the ignition cylinder. The transceiver then communicates the ID code to a vehicle electronic control unit (VCU) for validation and enabling of engine starting. Such a feature obviously helps deterring theft since the driver must be in possession of an ignition key with a compatible mechanical code plus a valid electronic ID code to be communicated to the vehicle control unit to activate the vehicle functions and drive away with the vehicle. Usually, these systems are first initialised by teaching the vehicle control unit the transponder ID code of an associated ignition key and thereafter require that same ID code to be communicated to the control unit to enable vehicle operation. Examples of such anti-theft systems are described in U.S. Pat. No. 5,555,863 delivered to Kokubu in 1996 and U.S. Pat. No. 5,818,330 granted to Schweiger in 1999.
Some variations to the above concept are known but all consist in communicating an electronic ID signal to a control unit in order to enable engine starting. For instance, in U.S. Pat. No. 5,184,584 (Cantrellxe2x80x941993) and U.S. Pat. No. 5,612,578 (Drewxe2x80x941997), an electrically resistive pellet is embedded into the ignition key and the ID signal is determined by the resistance value.
It shall be pointed out that in most of these systems, the vehicle engine can be started if one knows the ignition key electronic ID code and can communicate it to the vehicle control unit, while providing an electronic circuitry to control the vehicle function as in any common remote starting system. To drive the vehicle, however, the key must still be introduced into the ignition cylinder to activate the ignition switch and let the vehicle control unit (VCU) take over full vehicle control.
Resistive coded anti-theft systems can be bypassed relatively easily to enable remote engine starting as described U.S. Pat. Nos. 5,184,584 and 5,612,578. One merely has to measure and mimic the appropriate resistor value with a fixed or variable resistor connected to the input connector to bypass the anti-theft system and enable engine starting. Transponder based systems are much more difficult to bypass since it is practically impossible to read the key ID code. Therefore, only the vehicle or anti-theft system manufacturer can provide a system in which a given start enabling coded signal can be transmitted by either the ignition key transponder or a remote transmitting unit to enable starting of the engine from a distance without trigging the anti-theft system, as provided for instance in U.S. Pat. No. 5,818,330. In order to provide a still higher level of reliability, at least one vehicle manufacturer (Nissan) is using a dual electronic code protocol in addition to the usual mechanical coding of the ignition key. The vehicle control unit communicates a random password to be memorised by the ignition key transponder every time the ignition is cut-off. To start the engine the next time, the key must be inserted properly into the ignition cylinder, then the key ID code is verified and the transponder is finally asked by the VCU to communicate the last password received. Since that password is random and is only known by the VCU and the key transponder, a very high level of safety is thereby achieved.
The aforementioned systems are performing so efficiently that they cause a major problem to remote starter manufacturers and installers trying to retrofit a remote starting system on vehicles equipped with such transponder based anti-theft systems. Indeed, they must find a way to bypass the verification routine of the VCU and/or the transceiver, or mimic the coded signal and the possible password normally transmitted by the ignition key transponder to start the engine successfully. That shall be accomplished while preserving the normal operation and performance of the theft-deterrent system of the vehicle.
Most available solutions to the above problem merely reside in providing the vehicle control unit with a mimic of the signal normally communicated by the ignition key transponder. A basic way to do that is to use a valid electronic ignition key (mechanical code plus transponder) dissimulated in the vehicle and inductively coupled to the transceiver unit of the key cylinder assembly through induction coils and a relay contact. Therefor, when the remote starting system is activated through the remote transmitter, the relay is energised and the spare key becomes inductively coupled to the transceiver that can read the ID code transmitted from the key transponder and communicate it or a confirmation signal upon request from the VCU to enable engine starting. That technique suffers from three main drawbacks: 1) an expensive transponder coded key must be purchased from the vehicle manufacturer and validated by the vehicle control unit, 2) it is relatively easy for a thief, to find the hidden key and merely disconnect it and use it normally in the ignition cylinder to drive away with the vehicle, which practically eliminates the usefulness of the anti-theft system, if not worse, and 3) the installation is critical for proper operation; the key must be installed as near as possible to the key cylinder transceiver, the coils must be wound carefully and precisely and nevertheless the risks of malfunction remain high.
There is thus a need for an electronic pass-key module (PK module) which can be used to retrofit a remote starting system on a transponder based anti-theft system equipped vehicle, without adversely affecting the normal operation and reliability of said anti-theft system.
More specifically, in accordance wits the invention, there is provided a pass-key electronic module for enabling remote control of a function of a motor vehicle equipped with a key identity code verifying anti-theft system under control of a vehicle control unit connected to a key identity code receiving sensor through a data communication link and an enable line, comprising:
(a) a communication circuit enabling communications with the vehicle control unit through the data communication link;
(b) an input receiver circuit for receiving a command signal from a remote control system controller;
(c) a switching circuit for disabling the sensor from communicating with the vehicle control unit upon sensing of the command signal through the input circuit; and
(d) a memory circuit storing an operating program and an identity code subject to validation by the vehicle control unit.
The present invention also relates to a method for enabling remote control of a function in a motor vehicle equipped with a key identity code verifying anti-theft system under control of a vehicle control unit connected to a key identity code receiving sensor through a data communication link and an enable line, said method comprising:
(a) providing a pass-key electronic module with communication and switching capability, in which an identity code is memorized;
(b) connecting said pass-key module for communication with the vehicle control unit through the communication data link;
(c) connecting the pass-key module in series with the sensor enable line for controlled switching of the line;
(d) communicating the identity code to the vehicle control unit for validation of the identity code; and
(e) connecting the module to a remote control system controler output so that when a command signal is generated by the controller, the module switches the key identity code sensor enable line open, thus disabling the sensor, and communicates the validated identity code to the vehicle control unit which then enables a function in the vehicle.